To meet the demand for higher integration density and operating speed of LSIs, the effort to reduce the pattern rule is in rapid progress. As the advanced micropatterning technology, the ArF immersion lithography involving exposure through a liquid (typically water) held between a projection lens and a substrate is utilized. Besides, studies are being made on the multi-patterning of ArF lithography and the lithography using extreme ultraviolet (EUV) of wavelength 13.5 nm.
In these lithography processes, chemically amplified resist compositions are used. Among constituent units of the base resin, lactone ring-containing constituent units are important in forming patterns at a high resolution, as viewed from the standpoints of dissolution contrast and control of acid diffusion. Suitable compounds providing such constituent units include, for example, methacrylic compounds having a lactone unit such as butyrolactone, valerolactone, norbornanelactone or cyclohexanelactone, or sultone unit. Inter alia, a focus is put on the condensed ring lactone containing butyrolactone skeleton, specifically 7-methacryloyloxy-3-oxabicyclo[4.3.0]nonan-2-one, 8-methacryloyloxy-3-oxabicyclo[4.3.0]nonan-2-one, and a mixture thereof (Patent Document 1) and spiro[methacryloyloxynorbornane-2,3′-tetrahydrofuran-2-one] (Patent Document 2).